/Engine/Source/Editor/UnrealEd/Public/Elements/SMInstance/SMInstanceElementEditorWorldInterface.h
If you want to duplicate an array of elements that are potentially different types, you probably want to use the higher-levelUTypedElementCommonActions::DuplicateNormalizedElementsfunction instead.
virtual void DuplicateElements ( [TArrayView](API\Runtime\Core\Containers\TArrayView)< const [FTypedElementHandle](API\Runtime\TypedElementFramework\Elements\Framework\FTypedElementHandle) > InElementHandles, [UWorld](API\Runtime\Engine\Engine\UWorld) * InWorld, const FVector & InLocationOffset, [TArray](API\Runtime\Core\Containers\TArray)< [FTypedElementHandle](API\Runtime\TypedElementFramework\Elements\Framework\FTypedElementHandle) > & OutNewElements )